Preferred embodiments of the present invention deal with propulsion systems, and more particularly with an improved impeller or water jet system and method for propelling marine vessels such as yachts, trawlers and the like.
Marine vessels, such as yachts, trawlers, ships and boats, are known to use various propulsion systems. A conventional propulsion system includes a propeller or xe2x80x9cpropxe2x80x9d mounted underneath and/or behind the hull of the vessel on a driveshaft extending from an engine compartment. When the propeller is driven to provide thrust, the vessel is pushed forward; however, such systems suffer in efficiency since a propeller pushes some water in directions other than the preferred direction of thrust. Moreover, the extended propeller and drive shaft can impact objects or the ground, can be fouled in seaweed, lines or other debris, can develop marine growths or can impact other items such as sea creatures, potentially damaging the propeller or the object encountered. This can be particularly dangerous in yachts or similar sized boats where people may be swimming or diving near the vessel.
One alternative to a conventional propeller is an impeller propulsion system also known as a water jet system. An impeller system pulls water through a water intake opening (typically located underneath and towards the middle to stern of the vessel) and then forces it through a channel and out through a discharge opening to propel the vessel. An impeller system typically includes a propeller or pumping mechanism mounted within the channel which is used to accelerate and focus the water movement. The expelled water force or jet pressure pushes the vessel forward. Conventional impeller systems frequently suffer from high maintenance needs, turbulence and cavitation within the channel, and frequently require a larger engine capacity and/or an engine operating at higher rpm.
Further, in waves or chop, the vessel may move so that the water intake opening(s) are exposed to air, introducing air bubbles into the system, causing a sudden reduction in resistance. Excess air can result in a momentary release of the propeller, i.e. cavitation, allowing the engine to rev too quickly and potentially damaging the engine. Accordingly, there is a need for an improved propulsion system.
In conventional and impeller systems, the propeller and shaft are normally exposed to the ambient water whenever the vessel is afloat. This exposes the metal and equipment to rust, debris and marine growth resulting in increased maintenance costs, especially in salt water. Due to the mounting of the propeller and shaft under the hull or within a channel, maintenance and/or replacement is difficult. Moreover, in many such vessels, the propulsion equipment is not in use a large percentage of the time. Accordingly, it is also desirable to provide a propulsion system where exposure to ambient water is minimized and maintenance and service can be facilitated.
The present invention addresses these needs.
A preferred embodiment of the present invention provides a propulsion system mounted in the hull of a marine vessel. The system includes a conduit system with water intake openings defined in the port and starboard portions of the hull adjacent the bow and below the waterline of the vessel. A third water intake may be defined amidship in the vessel""s keel. A collection or mixing chamber is mounted within the hull. Water intake conduits conduct water from the water intake openings to the collection chamber. Water discharge openings are symmetrically defined in the stern of the hull. Water discharge conduits conduct water from the collection chamber to the water discharge openings. At least one impeller is mounted in each of the discharge conduits.
In an alternate preferred embodiment, the present invention provides a system for isolating an impeller propulsion system mounted within the hull of a marine vessel. At least one water intake opening is defined in the hull of the marine vessel. At least one water discharge opening is defined in the stern of the hull of the marine vessel. A conduit system extends from the water intake opening(s) to the water discharge opening(s). At least one water intake valve is selectively operable to prevent the flow of water through the water intake opening(s), and at least one water discharge valve is selectively operable to prevent the flow of water through the water discharge opening(s). The system may further include a pump connected to the conduit system, and operable to evacuate water from the system when the water intake and the water discharge valves are closed.
A further preferred embodiment of the present invention provides a feature allowing access to the impeller portion of a propulsion system mounted within a marine vessel. The impeller portion of the propulsion system is normally mounted in a conduit within the hull below the waterline. A conduit extension or access tube section diverges from the conduit with a first end in open communication with the conduit adjacent the impeller. The opposing end of the conduit extension extends above the level of the vessel""s waterline. A sealable hatch is mounted to the opposing end of the conduit extension and may be opened to service the impeller.
It is a preferred object of the present invention to provide propulsion system for a marine vessel.
It is a further preferred object of the present invention to provide an improved propulsion system which is safer and more efficient.
It is another preferred object of the present invention to provide an improved propulsion system with reduced and easier maintenance.
It is still another preferred object of the present invention to provide a propulsion system which may be stored in a dry state while the vessel is still in the water.
Further objects, features and advantages of the present invention shall become apparent from the detailed drawings and descriptions provided herein.